How to use Lambda in LINQ select statement

Question

I am trying to select stores using a lambda function and converting the result to a SelectListItem so I can render it. However it is throwing a "Type of Expression in Select Clause is Incorrect" error:

IEnumerable<SelectListItem> stores =
    from store in database.Stores
    where store.CompanyID == curCompany.ID
    select (s => new SelectListItem { Value = s.ID, Text = s.Name} );
ViewBag.storeSelector = stores;

What am I doing wrong?

EDIT:

Also, how do I convert Int to String in this situation? The following does not work:

select (s => new SelectListItem { Value = s.ID.ToString(), Text = s.Name} );
select (s => new SelectListItem { Value = s.ID + "", Text = s.Name} );

EDIT 2:

Figure out the Int to String conversion. It is so typical of Microsoft to forget to include an int2string conversion function. Here is the actual workaround everyone is using, with fully working syntax:

select new SelectListItem { Value = SqlFunctions.StringConvert((double)store.ID), Text = store.Name };

To call this situation absurd is an understatement.

Russ Cam · Accepted Answer · 2013-03-22 18:58:23Z

134

using LINQ query expression

 IEnumerable<SelectListItem> stores =
        from store in database.Stores
        where store.CompanyID == curCompany.ID
        select new SelectListItem { Value = store.Name, Text = store.ID };

 ViewBag.storeSelector = stores;

or using LINQ extension methods with lambda expressions

 IEnumerable<SelectListItem> stores = database.Stores
        .Where(store => store.CompanyID == curCompany.ID)
        .Select(store => new SelectListItem { Value = store.Name, Text = store.ID });

 ViewBag.storeSelector = stores;

answered Mar 22, 2013 at 18:58

Russ Cam

126k34 gold badges211 silver badges275 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

Bill Software Engineer Over a year ago

Can you please help me convert int to string? There seem to be no way for LINQ to Entity to convert int to string.

Russ Cam Over a year ago

@YongkeBillYu You mean like for example 5.ToString()?

Russ Cam Over a year ago

Can you create another question and show the code for what you are doing?

Kgn-web Over a year ago

@RussCam, if I am not wrong . Where(store => store.CompanyID == curCompany.ID) is of type Func<> lamda expression???

Russ Cam Over a year ago

@Kgn-web use Action<T> when you want to pass a delegate that doesn't return a value and Predicate<T> delegate where you need to return a boolean value; Predicate<T> was introduced in .NET 2.0, and generally Func<T, bool> is more often used, which was introduced in .NET 3.5 IIRC.

|

Justin Niessner · Accepted Answer · 2013-03-22 18:58:22Z

20

Why not just use all Lambda syntax?

database.Stores.Where(s => s.CompanyID == curCompany.ID)
               .Select(s => new SelectListItem
                   {
                       Value = s.Name,
                       Text = s.ID
                   });

answered Mar 22, 2013 at 18:58

Justin Niessner

246k40 gold badges416 silver badges546 bronze badges

Comments

Jon Skeet · Accepted Answer · 2013-03-22 18:58:08Z

17

You appear to be trying to mix query expression syntax and "normal" lambda expression syntax. You can either use:

IEnumerable<SelectListItem> stores =
        from store in database.Stores
        where store.CompanyID == curCompany.ID
        select new SelectListItem { Value = store.Name, Text = store.ID};
ViewBag.storeSelector = stores;

Or:

IEnumerable<SelectListItem> stores = database.Stores
        .Where(store => store.CompanyID == curCompany.ID)
        .Select(s => new SelectListItem { Value = s.Name, Text = s.ID});
ViewBag.storeSelector = stores;

You can't mix the two like you're trying to.

answered Mar 22, 2013 at 18:58

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Comments

Gurbaksh Singh · Accepted Answer · 2018-09-21 06:32:59Z

5

Lambda Expression result

var storesList = context.Stores.Select(x => new { Value= x.name,Text= x.ID }).ToList();

answered Sep 21, 2018 at 6:32

Gurbaksh Singh

491 silver badge2 bronze badges

Comments

2 revs · Accepted Answer · 2018-09-21 06:34:34Z

Using Lambda expressions:

If we don't have a specific class to bind the result:

 var stores = context.Stores.Select(x => new { x.id, x.name, x.city }).ToList();

If we have a specific class then we need to bind the result with it:

List<SelectListItem> stores = context.Stores.Select(x => new SelectListItem { Id = x.id, Name = x.name, City = x.city }).ToList();

Using simple LINQ expressions:

If we don't have a specific class to bind the result:

var stores = (from a in context.Stores select new { x.id, x.name, x.city }).ToList();

If we have a specific class then we need to bind the result with it:

List<SelectListItem> stores = (from a in context.Stores select new SelectListItem{ Id = x.id, Name = x.name, City = x.city }).ToList();

Collectives™ on Stack Overflow

How to use Lambda in LINQ select statement

5 Answers 5

7 Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

7 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related